The present invention relates to fins used in an integrated heat exchanger which is constituted by providing a plurality of heat exchangers achieving different functions at the front and the rear with the fins shared by the plurality of heat exchangers and a method for manufacturing the fins.
The heat exchanger disclosed in Japanese Examined Utility Model Publication No. H6-45155 comprises a first heat exchanger and a second heat exchanger that share common fins and are provided parallel to each other. In this heat exchanger, slits are formed in the linear portions of the fins located between the first heat exchanger and the second heat exchanger so that the heat conduction occurring between the fins located closer to the first heat exchanger and the fins located closer to the second heat exchanger is minimized.
In addition, the duplex integrated heat exchanger disclosed in Japanese Unexamined Patent Publication No. H3-177795 achieves an integrated structure in which a first heat exchanger and a second heat exchanger that operate at different temperatures share fins, with one or a plurality of notched portions for cutting off heat conduction between the two heat exchangers formed in the middle areas of the fins along the widthwise direction. The publication also discloses that the notched portions are constituted of a plurality of slits formed by alternately slitting the opposite ends of the fins along the heightwise direction.
However, the examples of the prior art quoted above pose a problem in that since the slits or the notched portions are formed by completely cutting off the portions that are to form the slits or the notched portions, the cuttings create more waste. There is another problem in that the dynamic strength of the fins themselves is compromised.
Accordingly, an object of the present invention is to provide fins in an integrated heat exchanger which effectively prevent heat transfer, do not create cuttings during their formation and achieve a high degree of dynamic strength, and a method for manufacturing these fins.
In order to achieve the objects described above, according to the present invention, in an integrated heat exchanger comprising a plurality of heat exchangers achieving different functions that share fins laminated alternately with tubes, a heat transfer prevention portion is formed at a bent portion of each of the fins located between tubes of adjacent heat exchangers. As a result, since the heat transfer prevention portion, which is formed in the area located between tubes at the bent portion of the fins to be bonded to the tubes, is located at the position closest to the tubes, heat conduction occurring due to the difference between their temperatures is efficiently prevented.
In addition, the heat transfer prevention portion should be preferably formed by folding back at least one portion of the fin. It is also desirable that the folded portion formed by folding back one portion of the fin be provided with at least one projected portion that projects out toward the opposite side from the bent portion of the fin. Thus, since the heat transfer prevention portion is formed by bending backward the portion located at the fin bent portion between the tubes, it is possible to prevent any cuttings from being discharged. In addition, since the folded portion is constituted of at least one projected portion, the dynamic strength of the fin is improved.
The fin manufacturing method according to the present invention for manufacturing fins utilized in an integrated heat exchanger comprising a plurality of heat exchangers achieving different functions that share fins laminated alternately with tubes comprises, at least, a slit formation step in which at least a pair of slits are formed over a specific distance from each other at an approximate center of a fin material with a specific width along the widthwise direction, a corrugating step in which the fin material is bent in a corrugated pattern so that a bent portion is formed at the position where the pair of slits have been formed in the fin material along the direction in which the fin material advances, a heat transfer prevention portion formation step, in which a heat transfer invention portion is formed by folding back the portion between the slits constituting the bent portion in the fin material in a direction opposite from the direction in which the bent portion is bent and a crest cutting step in which corrugated fins formed at a specific pitch are cut to achieve a specific number of crests. In addition, a pitch adjustment step for adjusting the pitch of the corrugated fins may be implemented as well. Furthermore, it is desirable to implement a louver formation step for forming louvers in the fin material concurrently with the corrugating step.
In this method, the fin material achieving a specific width wound around, for instance, an uncoiler, is drawn out to first undergo the slit formation step, in which a pair or a plurality of sets of slits are formed at an approximate center along the direction of its width, and then to undergo the corrugating step, in which it is corrugated so that the portions where the slits are formed constitute bent portions in the fin material. Then, in the heat transfer prevention portion formation step, the area between the slits constituting the bent portion of the fin material is folded back in the opposite direction from the direction in which the bent portion is bent, and in the pitch adjustment step, the pitch of the corrugated fins is adjusted. In the crest cutting step, the corrugated fins formed at the specific pitch are cut to achieve a specific number of crests, to manufacture the fins described above with a high degree of efficiency.
In addition, it is desirable to slacken the fin material between the slit formation step and the corrugating step so that no excess tension is applied to the fin material during the corrugating step.
The pitch adjustment step includes a pitch reducing process implemented to achieve a specific pitch in the corrugated fin material, an intermediate setting process and a pitch setting process. In order to achieve consistency in the fin pitch, fins are first formed at a pitch smaller than a specific pitch and then the fin pitch is gradually adjusted to achieve the specific pitch so that the pitch is prevented from becoming larger due to the restorative force of the fins.
Furthermore, the corrugating step and the heat transfer prevention portion formation step should be preferably implemented at the same time. It is desirable to perform the corrugating step by employing a pair of roll gears, each having a plurality of projected portions projecting out in the radial direction and indented portions formed between the projected portions that interlock with each other with the projected portions of one roll gear fitted into the indented portions of the other roll gear. Thus, since the fins and the heat transfer prevention portions are formed continuously at the same time by a pair of roll gears, the number of work steps can be reduced and, at the same time, the work efficiency is improved.
To explain the method of forming the heat transfer prevention portions in more specific terms, each of the pair of roll gears is provided with a heat transfer prevention portion forming indented portion at the tip of each projected portion located at the position corresponding to the area between the pair of slits in the fin material and a heat transfer prevention portion forming projected portion formed at the base of each indented portion located at a position corresponding to the area between the pair of slits, and the heat transfer prevention portions are each formed by bending the area between the pair of slits in the fin material in the opposite direction from the direction in which the other portion of the fin material is bent between the heat transfer prevention portion forming projected portion and the heat transfer prevention portion forming indented portion.